Challenge to the assumption of the unitary diurnal variation of the atmospheric electric field based on observations in the Indian Ocean, Bay of Bengal, and Arabian Sea

Measurements of the atmospheric electric field and conductivity made aboard a research ship, ORV Sagarkanya on her four cruises in the Bay of Bengal and the equatorial Indian Ocean, are reported. In contrast to the generally observed unitary diurnal variation, the 40-day average field curve shows a maximum around 1000 UT and a minimum at 0000 UT with a small secondary peak at 1900 UT. Diversity of the nature of field curves obtained on our different cruises demonstrates the variability of the curve when averaged over shorter periods. Magnitudes of the measured electric field and conductivity and the calculated values of air-Earth current are comparatively much smaller than that reported earlier over oceans. When considered with reference to the classical theory of the global electric circuit, our observations indicate a tendency to accentuate the effect of storm activity over Asia-Australia and Africa-Europe and to attenuate the effects of far-distant storms over the Americas